This invention relates generally to antennas and in particular to a lightweight patch radiator antenna for use in an airborne or spaceborne phased array antenna.
It is known in the art that a patch radiator consists of a conductive plate, or patch,. separated from a ground plane by a dielectric medium. When an RF current is conducted within the cavity formed between the patch and its ground plane, an electric field is excited between the two conductive surfaces. It is the ,fringe field, at the outer edges of the patch, that launches the useable electromagnetic waves into free space.
Patch elements are advantageous in phased arrays because they are compact, they can be integrated into a microwave array very conveniently, they support a variety of feed configurations, and they are capable of generating circular polarization. They also have the advantage of cost effective printed circuit manufacture of large arrays of elements.
For some applications a major drawback to the use of phased array antenna systems is their high cost because of the need for hundreds or thousands of antenna elements and associated transmit/receive circuitry. For other applications such as a spaceborne application, weight is a critical factor. Prior art materials used in patch radiator antennas, having a dielectric constant of approximately 2 such as a Teflon-fiberglass material known as Duroid 5880, may result in a considerable weight contribution to the total weight of an antenna depending on its size. Duroid is a registered trademark of Rogers Corporation of Chandler, Arizona. A patch radiator antenna using Duroid material is described in U.S. Pat. No. 5,008,681, "Microstrip Antenna with Parasitic Elements," issued to Nunzio M. Cavallaro et al., and assigned to Raytheon Company of Lexington, Massachusetts. The present invention of a lightweight patch radiator antenna reduces the weight drawback and thermal control considerations related to the array antenna surface coatings in spaceborne applications.